1. The Field of the Invention
The present invention relates generally to X-ray imaging systems, and more particularly to a vacuum-tube image intensifier incorporated within a miniaturized C-arm assembly of a mobile X-ray imaging system.
2. The Background Art
The particular field of extremities imaging refers to X-ray imaging of the smaller anatomical members such as arms, legs, hands and feet. Extremities imaging thus requires only a small imaging area which has prompted the long felt need for miniaturized X-ray devices capable of producing high quality images. As a result, the development of X-ray devices for extremities viewing has been driven by the competing purposes of economizing size and cost and maintaining high imaging quality.
Responsive mainly to the need for economizing size and cost, miniaturized X-ray apparatus have been developed which are much smaller and less expensive than conventional X-ray apparatus. For example, U.S. Pat. No. Bl 4,142,101 (Reexamination certificate issued Feb. 19, 1991 to Yin) discloses an X-ray imaging chain having an image intensifier which utilizes a fiber optic minifier in combination with a micro channel plate (MCP) intensifier. The fiber optic minifier can be made small enough to enable the production of X-ray images from an input area which is three to six inches in diameter. Designers have been able to utilize the fiber optic minifier to produce smaller X-ray devices appropriate in size for extremities imaging.
However, such prior art X-ray systems, while somewhat useful because of their smaller size, are nonetheless characterized by a number of distinct disadvantages. The fiber optic minifiers and MCP amplifiers used in miniaturized X-ray systems have not been able to produce state of the art optical imaging, ironically because the channels of the MCP amplifiers are too large. The resolution and contrast ratio of the X-ray image is limited by the number of channels present in the MCP amplifier. Simply put, the number of MCP channels and associated fiber optic fiber which can fit per corresponding square inch of input area is too small to produce state-of-the-art X-ray images.
The resolution and contrast which result from such miniaturized X-ray systems fall well below acceptable levels of quality. The high resolution X-ray images of intracorporeal anatomy necessary to a physician's ability to diagnose and treat patients have thus been sacrificed in favor of smaller size and lower cost. In addition, the extremities imagers of the prior art are difficult to maneuver and cumbersome to use.